November 13, 2004 is a date that Twins fans will remember. It's the date they traded A.J. Pierzynski for Joe Nathan, Fransisco Liriano and Boof Bosner.
At the time, Pierzynski was a solid, if unspectacular, catcher, having hit .301 up to that point for the Twins. Nathan was an emerging star for the Giants bullpen, going 12-4 with a 2.96 ERA. Liriano was moderately impressive in the San Fransisco farm system, as was Bosner.
By 2006, this was looking like one of the most lopsided trades in recent baseball history. Nathan went 7-0 with a 1.58 ERA and 36 saves as one of the best closers in baseball. Liriano went 12-3, 2.16 with 10.7 strikeouts per nine innings. Bosner was solid in the middle of the rotation, going 7-6 with a 4.42 ERA.
Overall, the three pitchers went 26-9 with a 2.73 ERA. The Twins looked like they had a second ace in Liriano (to put behind Johan Santana), a solid back-end pitcher in Bosner, and one of the best closers in the game.
Pierzynski hit .272 with 11 HRs and 72 RBI in one season in San Fransisco before being let go.
But a funny thing happened on the way to this trade going down as John Smoltz for Doyle Alexander.
Liriano got hurt at the tail end of 2006, missing almost all of the last two months of the season, and the entire postseason. Since then, he's been struggling, with a solid 2008 marred by a terrible 2009 . He's made only 36 starts since 2006, missing time with Tommy John surgery, and is currently 5-11 with a 5.29 ERA for Minnesota (and he gave up seven runs in two innings last night)
Bosner went 11-19, 5.44 in 2007 and 2008, and is, for all I know, out of baseball. The two pitchers combined have gone 22-34 with a 5.18 ERA since 2006 (not including Liriano's train wreck Monday).
Nathan has been a superb, lights-out closer, sporting a 1.61 ERA with 105 saves since 2006.
Ultimately, while the Twins still got the better of the deal, because, hey, it's Joe Nathan, I really can't say it was the world's most lopsided deal. The 2006 Twins won the AL Central but failed to win a single game in the postseason.
After 2006, Bosner and Liriano have had a relatively minimal impact on the Twins, possibly even detrimental. In essence, this trade has became Nathan for Pierzynski. Lopsided, yes. But baseball's version of Great Train Robbery? Not quite. Not any more.
Now this could change. Maybe Liriano can make his way back and become a solid pitcher. But this trade has definitely swung from "major advantage: Twins" to just "Advantage, Twins"
Let this serve as a warning: The true "winners" of trades are often not determined until years after they're made.